Devils and a Devil Slayer
by Voltaire The Second
Summary: With his best friend lost, Gray looks to an unexpected ally to find him. Unfortunately for Gray, Natsu is no longer in their dimension, and is now somewhere in the High School DxD dimension. How will our favorite Devil Slayer manage to fit in with a bunch of devils? And more importantly, just where is Natsu? And why is he so important to Zeref?


**Hey guys! So those of you who follow me must be thinking, "Hey Voltaire! This isn't Dragon and a Vampire!", and you'd be right in thinking that. The idea for this story just kind of came to me, and I just had to follow through with it. Rest assured that I am working on chapter 7 for Dragon and a Vampire, a lot of things have come up, and I haven't had a whole lot of time to work on it, but it is coming very soon, I promise. In the mean time, I made this for you guys to enjoy! **

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**Devils and a Devil Slayer **

**Chapter 1 **

"**Momento Mori**!" Mard Geer exclaimed. The demon guild master of Tartarus had trapped Natsu and Gray in his most powerful curse. The one he designed to kill Zeref himself. Mard was honestly surprised by the power and tenacity of the two human wizards. To be able to fight him in his released form on equal grounds was certainly an admirable feat, one certainly worthy of praise. But with this, he would end it. Dark mist began to surround the two slayers. The two began to look around erratically, panic evident in their eyes. Natsu tried igniting his body on fire, in an attempt to push the mist away, but found himself completely drained of his magic energy. Gray's physical exhaustion prevented him from moving, He felt as if the weight of the world was resting upon his shoulders. As the mist became thicker around them, the two found it harder to breathe, It was if some unknown force was crushing their lungs from the inside. The two fell to the ground, gasping for air. Natsu was the first to lose consciousness, most likely from fatigue from fighting Mard Geer so long by himself. Gray was resting on one knee. It was becoming harder and harder to breathe, The new Devil Slayer started coughing, his body spasming violently as he did so. In an attempt to cover his mouth, Gray felt a warm, sticky substance on his hand. Looking down, he saw it was blood.

His blood.

"No.." Gray choked out. He couldn't fail now. His guildmates were counting on him. He had a promise to keep to this father. He couldn't let them all down. But what could he do? He couldn't stand. His vision was fading in and out. The taste of his own blood was strong in his mouth. The very taste of the taste of the iron made him sick to his stomach. The taste was getting stronger as he kept coughing up more and more blood. It was getting harder and harder to breathe with each passing second. Looking up, he saw Mard Geer. A smug grin was plastered all over the demon's face as he began laughing hysterically.

"It ends here human. Die with the rest of your race. Die, knowing that you failed. Die, knowing that you came closer than anyone else in existence to killing me, the great Mard Geer!" Zeref's creation exclaimed. A surge of anger rushed through Gray's dying body. Through sheer force of will, the ice wizard managed to stand on his broken and battered legs. A white-blue aura surrounded him. The tattoo on his arm glowed the same color as his aura, before turning an inky black.

"I won't lose. Not to you. Not now, not ever." Gray growled out. The aura around him grew stronger. The ground around him started to freeze over, and cold winds that rivaled the arctic blew towards Mard Geer. However, the demon lord looked unimpressed.

"Is this your final stand? I'm not at all impressed. Your father could freeze an entire city with just a thought. You think a few cold winds will scare me? Please. You'll die a pathetic death, just like your father!" Mard Geer sneered. And with that, Gray snapped. His aura intensified again, instantly freezing everything around him. The winds became harsher, blowing the dark mist that previously surrounded him temperature around the two combatants dropped to subzero extremes. His Devil Slayer tattoo formed into a black, ink like substance and started covering the right side of his body. However, only a thin, black streak made its way to his face.

"For my guild, my friends, my family. I swear, I will defeat you Mard Geer!" Gray exclaimed. Mard Geer looked at the young man standing before him. A mere human, no older than 18 years, compared to his centuries of experience would normally be compared to an ant fighting an army of humans. But this boy stood before defiantly like so many others have. But unlike them, he possessed something in his eyes that no other fool that dared to stand before him had.

Resolve.

Mard Geer chuckled. Momento Mori would soon be completed. Perhaps he could entertain himself a little while longer.

"Then come. Come and meet your fate boy!" the winged demon exclaimed. Gray charged the demon with a speed that surprised even the demon lord himself. When the young wizard was in front of the Tartarus guild master, he slammed his fist straight into his gut. Mard Geer never saw it coming. The great demon keeled over in pain from the unexpected , Gray was far from grabbed Mard's head and brought his knee up, effectively slamming the demon's head into it. Dazed and confused, Mard grabbed his aching head. shaking off his pain,he threw a punch at Gray's head. It unexpectedly went through the slayer's head, catching Mard off guard A second later, "Gray" shattered into many pieces of ice.

"A clone.." Mard growled out, obviously annoyed by Gray's trick. A second later, a heavy kick to the head sent Mard skidding to the ground, several feet away. Gray walked towards the fallen demon slowly, staring him down. Mard Geer didn't understand. In just a few blows, Gray had crippled him. But how? How did this human possess such power?

"It's over." Gray said, a sense of finality clear in his voice. He then kicked Mard Geer over. Resting his foot on top of the demon's chest, he applied as much pressure to the area as he could.

"**Ice Devil's...Fury!**" Gray roared out. Dark blue energy surrounded by ice and snow launched out of Gray's mouth, straight down towards Mard Geer. The dark guild master roared out in pain as the blast struck him. The feeling of the cold was so intense, it actually burned his skin. The demon was actually starting to lose feeling in multiple places throughout his body. Looking down, he saw that Gray was freezing his body. Upon realizing this, Mard Geer began struggling, but found he could no longer move. His entire body was frozen up to his neck. The now helpless guild master looked up at Gray, who now wore a sadistically triumphant grin on his face. Gray then held out one hand as if he were now holding something.

"**Ice Devil's Zeroth Long Sword!**" Gray shouted. Upon uttering the spell, a long, thin sword made out of ice appeared in the slayer's hand. He pointed the tip of the sword towards Mard Geer's neck and pushed slightly, drawing blood Even though the sword was made out of ice, the point of the sword felt sharper than steel Gray's bangs covered his eyes as he raised the sword to his side.

"And with this, I'm one step closer to avenging my father's death. Say goodbye, Mard Geer!" Gray exclaimed. As he swung the sword down, an explosion went off behind him, causing him to lose his grip on his sword.

"What the hell?!" the raven haired man shouted. The mist that appeared because of Mard Geer's curse, Momento Mori,had apparently reappeared, and was now 's eyes widened in fear and realization, as he head forgotten something in his rage. A friend he had left behind.

"Natsu!" Gray yelled out of fear and desperation. Forgetting his trapped prey, Gray ran over to the site of the explosion. While running, the ink-like black markings slowly receded back into his tattoo. Reaching his destination, a now barren area with a small crater marking the area with burn marks and cracks marking the land, Gray's fear and anxiety grew. Gray saw no trace of Fairy Tail's Fire Dragon Slayer.

"No.." Gray whispered. A lone tear fell down his face. Behind him, he heard Mard Geer laughing.

"Even in defeat, I still win. Even in victory, you still lose, Fullbuster." Mard Geer coughed out. Gray started shaking. Not because he was sad. Not because he was scared. No, there was only one emotion he was feeling.

Hatred.

Hatred for the one who killed his best friend.

He turned around and walked briskly towards Mard Geer, fury clear in his expression. His dark blue eyes were now close to black, and the ink like markings from his tattoo started to cover his body again, this time, at even faster rate. When he arrived next to Mard Geer's frozen body, he grabbed the guild master by his neck, applying as much pressure to it as he possibly could.

"You don't deserve a quick death…: Gray said lifelessly, almost with no emotion. Mard was now gasping out for air, but the smirk never left his face, further infuriating Gray. Just as Gray was about to finish him, he pulled off of Mard Geer by someone. Gry figured it was one of his guild mates, seeing how they had a no killing policy. As he got up, he was shocked by who he saw. It wasn't Master Makarov. It wasn't Erza or Gajeel. No, it was far worse than that. Standing before him was the world's most powerful dark wizard. He wore a black robe covered by a white cloth. His eyes were a piercing blood red, and his wild but kept black hair swayed in the wind.

It was Zeref.

Gray stood there, awestruck. His eyes widened in fear. He couldn't even move. Zeref's presence alone was extremely intimidating. Zeref however, did not look menacing. Rather, he looked displeased, even annoyed.

"Master…" Mard Geer whispered. The near frozen demon's head was shaking, either out of some fear driven respect, or just out of fear. Zeref's displeased expression intensified into one of anger. A menacing black and white aura appeared around Zeref, and his gaze hardened upon looking down at his creation. Without a word, he held his hand out and opened it. A sphere of black energy appeared in the palm of his hand. Mard Geer, realizing what was about to happen, panicked.

"Master, please, no!" Just give me another chance!" the once proud demon begged. Zeref simply sighed in disappointment. The sphere of energy launched from his hand, killing Mard Geer instantly. Gray, shocked by this display of brutality, took an involuntary step back. However, this caught Zeref's attention. The dark wizard walked away from the lifeless corpse of his former servant to the terrified devil slayer. However, upon getting within arm's length of Gray, the displeased look on Zeref's face turned into a melancholy smile.

"Gray Fullbuster, yes?" the dark wizard asked politely. Gray, understandably caught off guard by this seemingly out of character display, nodded dumbly. Zeref seemed to chuckle at this.

"No need to be serious Mr. Fullbuster. I have not come to hurt you whatsoever. I do require a favor, however. Zeref said seriously. Again, Zeref had caught Gray off guard. Zeref was supposed was to be the world's most powerful and brutal dark wizard. Why the hell was he acting so formal and polite? It didn't make any sense. Shaking off his confusion, Gray's eyes narrowed in suspicion.

"And why should I help you?" Gray sneered. Zeref sighed. He expected something like this. He wasn't evil. His magic was directly tied into his magic. All these years of killing, creating the etherious demons...he never wanted to. His magic got the better of him, and it still does. Shaking his head of these thoughts, he looked at Gray.

"I can help you find Natsu." Zeref replied honestly. Gra's eyes widened at this.

"Where is he?"

"Agree to help me, and I'll tell you." Zeref countered. Gray growled in response. He'd rather not help the world's most infamous wizard, especially because it was Zeref who created the demons that caused him, his friends, and his family so much pain in the past. But he had to find Natsu, no matter what the cost. Gray sighed in defeat.

"Fine, I'll help you, But don't you dare try anything funny." Gray growled out. Zeref's melancholy smile returned as he nodded his head.

"Of course, Mr. Fullbuster. Now, as for my favor, it coincides with your goal. I want you to find Natsu." Zeref explained. Gray looked at the dark wizard suspiciously.

"Why would you want me to do that?" Gray asked. This didn't make any sense. Nothing about this situation did. Zeref, the world's most powerful and deadly dark wizard, was being polite and helpful towards Gray, who had killed some of his strongest demons. And why would Zeref want Gray to save Natsu? What was his goal?

"That's none of your concern." Zeref snapped. Gray jumped at the sudden change in his tone. Getting into a fight with a man who could kill him with a single thought was not on Gray's "to-do" list. Seeing that he momentarily lost control, Zeref took a deep breath to calm himself.

"Sorry. All you need to know is that Natsu is very important." Zeref explained. Gray look at the ageless man skeptically, but nodded. He wasn't wrong. Natsu was in fact very important. Natsu was the heart of Fairy Tail. No matter how much Gray hated to admit it, Natsu was one of Gray's closest friends Gray sighed.

"Alright, where do I find him?" Gray asked. Zeref's smile faltered for a second. Gray noticed this and looked at the man strangely.

"Well you see, that's where things get complicated…"

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**So I hope I kept the characters as in character as I could. I changed things up a bit for the fight, and also, keeping in mind Gray's new personality, I tried to through some of that in as well. The crossover starts next chapter, which I can hopefully get up for your reading pleasure soon. I don't have any set pairings in mind. so leave me your thoughts on that. Be sure to leave me a review to let me know what I screwed up, what I did great on, and what I could improve on! Also, point out any grammatical errors to me so I can fix those ASAP. Be seeing you guys real soon! Have a day!**


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